This invention relates to a recorded data reproducing apparatus, which can accurately read data from any track or cylinder of a recording medium, based on servo data recorded on the medium.
Because of the necessity for accurately positioning a read head on a target track, a recorded data reproducing apparatus needs to ensure that a signal corresponding to servo data is at a constant level. Conventional recorded data reproducing apparatuses have an AGC amplifier which amplifies a signal read by the read head and has a gain data input terminal. The gain of the AGC amplifier is varied in accordance with gain data supplied to the gain data input terminal. This gain data is generated by an AGC generator based on the output of a differential circuit provided at the succeeding stage of the AGC amplifier. The AGC generator is constituted by complex circuits, such as a rectifier/smoothing circuit for averaging the output of the differential circuit, an amplifier and a level shifter. Therefore, complicated adjustment of the AGC generaoor is required in the manufacturing process. This increases the manufacturing cost of a recorded data reproducing apparatus.